The present disclosure discloses a magnetic head, a head gimbal assembly, a hard disk drive, and a method for processing a magnetic head. The method comprises irradiating at a fixed point proximal to the read/write part with a laser irradiation device until the read head and the write head are thermally expanded; orientating air bearing surfaces of a plurality of magnetic heads forming a magnetic strip toward a lapping surface of a lapping device after laser irradiation, holding the air bearing surfaces in place, lapping with the lapping device until the air bearing surfaces are coplanar; and disassembling the magnetic strip to obtain a lapped magnetic head. Through laser heating induced compensation, the heights of lapped read head and write head of the magnetic head meet their respective target values, ensuring the normal reading and writing of the storage medium of the magnetic disk.